This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A086417 #19 Jul 16 2021 06:35:59 %S A086417 1,3,4,7,12,15,13,28,31,39,60,40,63,91,124,120,127,195,121,252,280, %T A086417 255,403,363,508,600,364,511,819,847,1020,1240,1092,1023,1651,1815, %U A086417 1093,2044,2520,2548,2047,3315,3751,3279,4092,5080,5460,4095,3280 %N A086417 Sum of divisors of 3-smooth numbers. %H A086417 Reinhard Zumkeller, <a href="/A086417/b086417.txt">Table of n, a(n) for n = 1..10000</a> %F A086417 a(n) = A000203(A003586(n)); %F A086417 a(n) = (2^(A022328(n)+1)-1)*(3^(A022329(n)+1)-1)/2. %F A086417 a(n) = A000225(j) * A003462(k) for some j,k > 0. - _Flávio V. Fernandes_, May 29 2021 %t A086417 DivisorSigma[1,#]&/@Select[Range[4000],Max[FactorInteger[#][[All,1]]]<4&] (* _Harvey P. Dale_, Feb 14 2017 *) %o A086417 (Haskell) %o A086417 a086417 n = (2 ^ (a022328 n + 1) - 1) * (3 ^ (a022329 n + 1) - 1) `div` 2 %o A086417 -- _Reinhard Zumkeller_, Nov 19 2015 %Y A086417 Cf. A086416. %Y A086417 Cf. A000203, A003586, A022328, A022329. %K A086417 nonn %O A086417 1,2 %A A086417 _Reinhard Zumkeller_, Jul 18 2003